The field of the disclosure relates generally to airfoils and, more particularly, to airfoils for rotary machines that include a propeller assembly.
At least some known rotary machines are gas turbine engines used for propelling an aircraft in flight. Some known gas turbine engines include a combustor, a compressor coupled upstream from the combustor, a turbine, a rotor assembly rotatably coupled between the compressor and the turbine. At least some known aircraft engines include at least one airfoil that is moved through fluid to produce an aerodynamic force. For example, some known rotary machines include a propeller assembly drivingly coupled to the rotor assembly. The rotor assembly rotates to drive the propeller assembly and, thereby, move air to propel the aircraft. Rotation of the propeller assembly also generates tip flow structures, which cause noise and aerodynamic inefficiencies.
To increase an operating efficiency, some known rotary machines include winglets on blades of the propeller assemblies to inhibit air flowing over the tip of the blade and, thereby reduce the generation of flow structures. The winglets project from each blade at or very near the tip of the blade and form a change in direction along a surface of the blade. However, the change in direction sometimes generates flow patterns that increase a noise level of the rotary machine during operation.
Some known aircraft engines include two or more propeller assemblies that interact to move air and, thereby, propel an aircraft. The interaction of the propeller assemblies generates flow structures, which cause operating inefficiencies. Accordingly, some aircraft engines include fences attached to the blades of the forward propeller assembly to reduce the operating inefficiencies caused by the interaction of the propeller assemblies. However, the two or more propeller assemblies are not configured for use in rotary machines having a single propeller assembly, such as unducted single fan propulsion systems and turboprop engines.